Wireless communication systems capable of supporting multiple types of communication services are known in the art. For example, U.S. Pat. No. 5,548,631 entitled METHOD AND APPARATUS FOR SUPPORTING AT LEAST TWO COMMUNICATION SERVICES IN A COMMUNICATION SYSTEM, issued Aug. 20, 1996 to Krebs et al. and assigned to Motorola, Inc., describes a communication system that supports both telephone and dispatch services. Dispatch services and telephone services differ in a variety of ways from one another, and certain problems can be encountered when providing common infrastructure to support both services. For example, regardless of which service is requested, sufficient communication resources (typically, radio frequency (RF) channels, time slots, etc.) may not be available to immediately support the request. When this occurs in a dispatch context, the request is typically queued indefinitely and the dispatch user is notified upon subsequent availability of the required resource. Contrary to this, a request for a telephone call is typically not queued and the telephone user is not subsequently advised of resource availability. Although these methods of operation are in accordance with user expectations, they can lead to inefficiencies in system resource utilization.
In particular, in a wireless communication system using shared resources in which one or more services are queued and one or more services are non-queued, over time the queued service(s) will tend to monopolize system resources as they become available. As a result, the perceived quality of service for the non-queued services, particular with regard to service availability, decreases. To illustrate using the dispatch/telephone system described above, because dispatch requests are queued, they will tend to occupy all available system resources given that the "persistence" of telephone requests is negligible in comparison. U.S. Pat. No. 5,457,735 entitled METHOD AND APPARATUS FOR QUEUING RADIO TELEPHONE SERVICE REQUESTS, issued Oct. 10, 1995 to Erickson and assigned to Motorola, Inc., describes a solution to this problem in which telephone requests are queued for a finite period of time, thereby increasing the probability that such requests will be provided resources. Additionally, U.S. Pat. No. 4,612,415 entitled DYNAMIC CONTROL OF TELEPHONE TRAFFIC IN A TRUNKED RADIO SYSTEM, issued Sep. 16, 1986 to Zdunek et al. and assigned to Motorola, Inc., describes another solution in which dispatch access delay is continuously measured over succeeding 15 minute intervals. Based on the dispatch access delay measured during a prior 15 minute interval, a number of communication resources reserved to support dispatch service is adjusted for the next 15 minute interval. This process is continuously repeated while the system is in service.
Still another approach to this problem is to partition the system resources in a predetermined manner so that no one service can dominate the resources at the expense of the other services. In one approach referred to as "hard" partitioning, the resources are partitioned in accordance with historical usage of the respective services such that requests for each type of service can only be fulfilled from the designated portion of resources. For example, if, in a given system, 70% of system capacity is historically used to service dispatch requests, with the remaining 30% used to service telephone requests, the system resources will likewise be partitioned on a 70/30 basis. This works well so long as the actual system load stays at 70% dispatch and 30% telephone. However, should the amount of dispatch requests decrease, the otherwise unused resources assigned to support dispatch cannot be used to support an increase in telephone services. Conversely, should the amount of dispatch requests increase, the system cannot assign additional resources to support the increased requests. These inefficiencies likewise apply to increases and decreases in telephone requests.
A somewhat "softer" variant of hard partitioning is to always maintain a minimum number of resources for a given service. For example, at system set-up, the resource allocator in the system would be configured to ensure that no less than N resources (where, typically, N&gt;1) are available and/or in use to support a given service. As a result, the given service will always be guaranteed a minimum level of resources for use in supporting requests for that service, thereby ensuring at least a minimum level of service at all times. Should the number of requests for that service increase such that the N resources are not enough to support all requests immediately, the system is free to assign additional resources, if available, to service the additional requests. However, it is still possible that there are more than enough reserved idle resources to meet the demand for that service at any given time. As a result, resources that may be put to better use in support of other services remain unused in order to maintain the required minimum number for the given service. In effect, both the hard partitioning and minimum number methods work well so long as the offered system load at any given time matches the historical load upon which the partitioning/minimum thresholds are based, but both introduce inefficiencies when the offered load varies from the historical basis.
The problems described above are further exacerbated when the communication resources themselves provide varying grades of service and where different services require communication resources having minimum grades of service. This is particularly true where requests for non-queued services must be fulfilled using resources having a higher grade of service and where requests for queued services may be fulfilled using either lower or higher grade resources. Therefore a need exists to better accommodate the ability of non-queued services to obtain requested resources in a multi-service shared infrastructure communications system.